riscv: Fix set_huge_pte_at() for NAPOT mapping

As stated by the privileged specification, we must clear a NAPOT
mapping and emit a sfence.vma before setting a new translation.

Fixes: 82a1a1f3bfb6 ("riscv: mm: support Svnapot in hugetlb page")
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240117195741.1926459-2-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/mm/hugetlbpage.c b/arch/riscv/mm/hugetlbpage.c
index 431596c0e20e04e1ad5a2422fa989f27cdfdc7c4..865ac5c7d159e682a5afb7fe489eda9ca3152d8f 100644 (file)
--- a/arch/riscv/mm/hugetlbpage.c
+++ b/arch/riscv/mm/hugetlbpage.c
@@ -177,13 +177,36 @@ pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
        return entry;
 }
 
+static void clear_flush(struct mm_struct *mm,
+                       unsigned long addr,
+                       pte_t *ptep,
+                       unsigned long pgsize,
+                       unsigned long ncontig)
+{
+       struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
+       unsigned long i, saddr = addr;
+
+       for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
+               ptep_get_and_clear(mm, addr, ptep);
+
+       flush_tlb_range(&vma, saddr, addr);
+}
+
+/*
+ * When dealing with NAPOT mappings, the privileged specification indicates that
+ * "if an update needs to be made, the OS generally should first mark all of the
+ * PTEs invalid, then issue SFENCE.VMA instruction(s) covering all 4 KiB regions
+ * within the range, [...] then update the PTE(s), as described in Section
+ * 4.2.1.". That's the equivalent of the Break-Before-Make approach used by
+ * arm64.
+ */
 void set_huge_pte_at(struct mm_struct *mm,
                     unsigned long addr,
                     pte_t *ptep,
                     pte_t pte,
                     unsigned long sz)
 {
-       unsigned long hugepage_shift;
+       unsigned long hugepage_shift, pgsize;
        int i, pte_num;
 
        if (sz >= PGDIR_SIZE)
@@ -198,7 +221,22 @@ void set_huge_pte_at(struct mm_struct *mm,
                hugepage_shift = PAGE_SHIFT;
 
        pte_num = sz >> hugepage_shift;
-       for (i = 0; i < pte_num; i++, ptep++, addr += (1 << hugepage_shift))
+       pgsize = 1 << hugepage_shift;
+
+       if (!pte_present(pte)) {
+               for (i = 0; i < pte_num; i++, ptep++, addr += pgsize)
+                       set_ptes(mm, addr, ptep, pte, 1);
+               return;
+       }
+
+       if (!pte_napot(pte)) {
+               set_ptes(mm, addr, ptep, pte, 1);
+               return;
+       }
+
+       clear_flush(mm, addr, ptep, pgsize, pte_num);
+
+       for (i = 0; i < pte_num; i++, ptep++, addr += pgsize)
                set_pte_at(mm, addr, ptep, pte);
 }